It is well known that a number of ion channels are involved in the proliferation, migration and invasion of tumor cells. TASK channels, an acid-sensitive subgroup of the two-pore-domain K+ channel (K2P) family, are expressed in numerous types of tissue and exhibit various physiological functions depending on the cell type. In the present study, we employed RT-PCR and western blot analysis to determine the expression of TASK-1, -2 and -3 at the mRNA and protein levels in MG63 human osteoblast-like cells. Immunofluorescence with specific antibodies against the TASK channels revealed the localization patterns at the plasma membrane and the juxtanuclear compartment. The induced fluctuations in the extracellular pH from 7.4 to 6.9 and to 6.4 significantly reduced the proliferation rate of MG63 cells by 44.3 and 90.1%, respectively. These data revealed the expression of TASK-1, -2 and -3, and the correlation between TASK channels and cell proliferation in MG63 cells, suggesting that these channels may be involved in the tumorigenesis of osteosarcoma.